1. Field of the Invention
The present invention relates to a technology to separate and analyze nucleic acids, proteins and the like by means of electrophoresis and, for example, relates to a capillary electrophoresis unit.
2. Description of the Related Art
An electrophoresis method using capillaries has been used for the purpose of determining a base sequence and base length of DNA and the like.
The multi-focus method described in U.S. Pat. No. 5,582,705 is known as one of light irradiation methods to a plurality of capillaries. In this method, a capillary on one end of a capillary array consisting of a plurality of capillaries arranged in parallel on a plane substrate or capillaries on both ends of the capillary array are irradiated with a laser light and luminescence generated in the capillary array while the laser light crosses the capillary array by propagating successively from one capillary to the adjacent one is detected by a photodetector. A test sample containing DNA labeled by fluorescence dye is introduced into the capillaries and a laser light is shone in such a way that the laser light propagates through the plurality of capillaries arranged in rows. Laser light shone on the capillaries causes the fluorescence-labeled DNA to generate fluorescence. By measuring fluorescence from each capillary, DNA analysis of the test sample introduced into each capillary can be performed. Proteins and the like can also be analyzed in a similar fashion.
Intensive discussion by the inventors of the application concerned revealed a problem described below.
In order to measure a plurality of samples simultaneously by the method disclosed in U.S. Pat. No. 5,582,705, test sample concentrations must be limited to the dynamic range of an electrophoresis apparatus. Thus, for gene sequencing analysis using electrophoresis, normally time is taken in purifying test samples in a step of electrophoresis pretreatment to prepare approximately uniform test sample concentrations before analyzing such test samples. For example, concentration checks by RNA are done before test samples are set to an electrophoresis apparatus.
However, if the current electrophoresis apparatus is applied to the field of clinical gene function analysis, it is anticipated that samples which do not undergo the adequate pretreatment process will also be measured. For example, it is anticipated that the amount of sample is too small to do concentration checks and thus samples are directly set to an electrophoresis apparatus without doing any concentration check, or samples made to have higher concentrations in advance for expression analysis are analyzed. If, when analyzing a sample whose concentration is not known, the dynamic range of an apparatus is insufficient, a measured signal value may exceed the limits of detection during analysis. In that case, an analyst adjusts the voltage and time when the sample is put in and controls the amount of sample to perform the analysis again.
An object of the present invention relates to suitably analyze a sample even if a concentration thereof is not known.